Helenius found the net for the first time for Villa on FA Cup third round weekend in the defeat to Sheffield United, and was prolific for Aalborg in Denmark before his £1.2million move to the Midlands.
The Villa manager has since brought Holt in from Wigan - but Lambert insists Holt's arrival is not the end for Helenius.
"Holty will bring experience. He's streetwise. He'll get you free-kicks where maybe a younger player might not be able to do that for you at the minute," he told the Express and Star website.
On Helenius, Lambert added: "He's not frustrated, that's one thing Nicklas is not. If you watch Helenius finish in training he very rarely misses the target. He's a young guy and he's learning."